As more and more capability is being designed into semiconductor devices, such as memory modules and microprocessors, there are an increasing number of leads or input/output elements being placed onto electronics packages. In the past, peripherally leaded packages provided an adequate number of leads or input/output elements. Peripherally leaded packages have leads or input/output elements along the edges of the electronic component. In many applications, such packages provide an adequate number of input/output elements. In the past few years, however, many semiconductor devices have required more input/output elements than provided in a peripherally leaded package.
To provide additional electrical contacts for a semiconductor device, many have used a grid array package. In a grid array package the input/output elements are placed on the surface of the semiconductor devices. The grid array packages have many advantages, including simplicity, high contact density, and extremely low inductance due to the short paths between the contact and the element within the semiconductor device. There are several types of grid arrays. Ball grid arrays and chip scale packages have hemispherical solder balls as input/output elements. Pin grid arrays have gold plated pins as input/output elements. Land grid arrays have flat, gold plated pads as input/output elements.
In general, the grid array packages are lower cost solutions than the peripherally leaded packages. Of the grid array packages, the most simple and least costly is the land grid array package. Most of the grid array packages have been successfully implemented in products. However, the land grid array packages have technical limitations that stand in the way of wide acceptance of this technology in a useable product. The technical limitations include the fact that land grid array packages have limited current carrying capability. Currently, the lands of the land grid array are used either to carry input/output signals or to carry power. Simply put, the capability of the individual lands to carry power is limited due to the small size of the land grid array and the electrical connections made to the land grid array. This limits the amount of power that can be input to such packages.
Another technical problem with land grid array packages is that there is a short wiping distance between the land and the contact as the contact is initially placed in contact with the land. The wiping distance is the length of travel between an individual land or pad of the land grid array and the contact which is placed in electrical communication with the pad. Generally, longer wiping distances are preferred since the longer wiping distance tends to insure penetration of any oxide layer on the individual land or pad, so that a good electrical contact is made.
There is a growing demand for high loads and evenly distributed loads on a die package. Current land grid array packages have difficulty in handling a high load and difficulty in distributing the load on the packages evenly. This lacking is yet another technical hurdle that stands in the way of acceptance of land grid arrays becoming a widely used packaging technique in various products.
Thus, there is a need for a land grid array packaging method and apparatus that allows the simple, high contact density, low inductance land grid array solution to become widely used. There is a need to overcome the limited current carrying capability of the land grid array package. There is a further need to lengthen the typical short wiping distance to assure reliably good electrical contact between the contacts and the individual lands. There is also a need to meet the demand for high and evenly distributed die loads.
The description set out herein illustrates the various embodiments of the invention and such description is not intended to be construed as limiting in any manner.